A light-emitting module of a common lamp device used in an office or factory, especially that of a light-emitting diode lamp device, cannot be easily changed, as the lamp device is usually designed to be an integral piece. Therefore, a user cannot merely replace a light-emitting module therein when the light-emitting module is broken. Rather, the entire device must be replaced. Also, a user cannot change the type (e.g., for different brightness) of the light modules according to requirements, which may cause practical inconvenience for a user.